In recent years, an IP telephone system has come into wide use. For example, according to the IP telephone system, an IP telephone terminal is connected to an IP network including a local area network (LAN) and Internet. A call control server on the IP network executes a protocol conversion and a data format conversion. In this way, voice communication is possible between IP telephone terminals and an IP telephone terminal and a general telephone network.
In general, the foregoing call control server includes a controller using a microcomputer. The controller collectively controls the operation of the call control server. Moreover, the controller includes a system startup program such as an operating system (OS) on control hardware. The controller executes a service program given as a communication control application program on the OS environment, and thereby, is configured to operate hardware.
In the foregoing call control server, the system startup program and the service program starts up in a memory area, which is the same program execution environment. For this reason, the failure of the service program gives an influence to the system startup program and a system startup processing; as a result, the system startup becomes incomplete.